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Dynamics of infection and pathology induced by the aporocotylid, Cardicola laruei, in spotted seatrout, Cynoscion nebulosus (Sciaenidae)

journal contribution
posted on 2023-05-20, 17:53 authored by McElroy, EJ, Barbara NowakBarbara Nowak, Hill-Spanik, KM, Granath, WO, Connors, VA, Driver, J, Tucker, CJ, Kyle, DE, de Buron, I

The sciaenid Spotted Seatrout (Cynoscion nebulosus) are infected by blood flukes (Cardicola spp.). A 2 year survey in estuaries of South Carolina, USA, showed that adult flukes and granulomas occurred throughout the year but their prevalence was highest in summer (61% and 84%, respectively), indicating an unusually high level of infection for wild fish. Granulomas remained after adult flukes could no longer be found. PCR-Restriction Fragment Length Polymorphism (RFLP) of a subsample of specimens allowed identification of Cardicola laruei as the only species infecting these seatrout during the period of study. Mean intensity of infection by flukes was higher in female seatrout, suggesting endocrine and/or immune system involvement. The prevalence of granulomas declined sharply in winter, indicating possible mortality of infected seatrout as this species is known to be cold-sensitive. Granulomas were studied using histology, immunohistochemistry, and transmission electron microscopy. Eggs were encapsulated by an inner core of dark epithelioid cells, and an outer core of large epithelioid cells undergoing epithelialization. Fibrosis was observed around granulomas and some granulomas detached from the surrounding damaged myocardium. Numerous inflammatory cells appeared mobilised around granulomas and pathology could be severe, in some cases showing grossly visible blister-like extrusions scattered in the damaged epicardium. At the gross level, some granulomas possessing eggs with live miracidia were observed at the surface of the epicardium. These findings suggest that granulomas carrying both dead and live eggs can clear the fish heart by host-mediated transport through the myocardium, as is known to occur in related human Schistosoma infections.

History

Publication title

International Journal for Parasitology

Volume

50

Issue

10-11

Pagination

809-823

ISSN

0020-7519

Department/School

Institute for Marine and Antarctic Studies

Publisher

Pergamon-Elsevier Science Ltd

Place of publication

The Boulevard, Langford Lane, Kidlington, Oxford, England, Ox5 1Gb

Rights statement

Copyright 2020 Australian Society for Parasitology.

Repository Status

  • Restricted

Socio-economic Objectives

Aquaculture fin fish (excl. tuna)

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